1. Field of the Invention
The present invention relates to Global System for Mobile Communications (GSM) systems and, in particular, to a signal transmission method and apparatus of a base station for increasing transmit power by compensating phase value of the signal transmitted through multiple antennas based on signal reception status information fed back from a terminal in the GSM system.
2. Description of the Related Art
In radio communication systems, multiple antennas may be used in various transmission techniques such as beamforming with multiple transmit antennas, receive diversity with multiple receive antennas, and transmit diversity with multiple transmit antennas, for improvement in coverage range, capacity, and/or reliability. The transmit diversity techniques can be classified into Space-Time Block Code (STBC) and Transmit Delay Diversity (TDD) techniques. Typically, the GSM system adopts the TDD technique with the configuration as depicted in FIG. 1 to expand the coverage.
FIG. 1 is a block diagram illustrating the configuration of a base station transceiver of a conventional GSM system with TDD.
Referring to FIG. 1, the base station transceiver includes a first antenna 10, a second antenna 12, a first power amplifier 14, a second power amplifier 16, and a delay 18.
The first and second antennas 10 and 12 are capable of transmitting base station signals to a terminal and receiving signals transmitted by the terminal. The first and second power amplifiers 14 and 16 supply power to the first and second antennas 10 and 12, respectively. The delay 18 is capable of being set to a value for delaying the signal to be transmitted through the second antenna 12. In the conventional GSM system, it is possible to increase the transmit power with multiple transmit antennas but no coherent combining among multiple signals, and thus it is difficult to expect 100% of multiple antenna gain.
There is therefore a need for a method for improving coherent combining gain in the GSM system.